Depositional and postdepositional processes in the magnetization of sediments

Abstract

This paper surveys 40 years of research on the processes by which a sediment acquires a detrital remanent magnetization (DRM). These processes can be divided into two types: depositional processes, which arise from interactions between the magnetic carriers and the substrate at the sediment/water interface, and postdepositional processes, which arise from the mobility of magnetic carriers within fluid‐filled voids in the sediment. Depositional DRM is well understood theoretically and experimentally, but its applicability to natural sediments may be quite limited. Postdepositional DRM, which has not been studied in sufficient detail, may well be the dominant process by which sediments acquire a magnetization. The nature and composition of both the magnetic carriers and the matrix as well as the pore water content of the sediment influence the balance between depositional and postdepositional DRM. The identification of the method of magnetization in a given sedimentary environment, such as glacial lakes, the deep sea, or lakes and marginal seas, can be a difficult problem. Since postdepositional DRM accurately records the ambient geomagnetic field, whereas depositional DRM does not, such an identification is necessary in order to use the detrital remanent magnetism of sediments in studies of the fine scale behavior of the geomagnetic field, the paleomagnetic correlation between sedimentary environments, and the possible relation between paleomagnetic parameters and paleoclimatic indicators.